(1) Field of the Invention
The present invention relates to a process for the preparation of a composition comprising a mixture useful as a diesel fuel or fuel oil. In particular, the present invention relates to a process which enables production of the composition without the need for an intermediate separation (extraction) step to remove a glycerol by-product from transesterification of a triglyceride, such as vegetable oil.
(2) Description of the Related Art
Biodiesel is rapidly gaining momentum as the next major biofuel for energy sustainability. Biodiesel production in Europe is already on the order of one billion gallons annually, but U.S. production is only 100 million gallons per year. However, the recent spike in petroleum prices, the increasing environmental awareness of U.S. consumers, and the October, 2004 passage of the biodiesel tax incentive (H.R. 4520) by Congress, providing a $1.00 per gallon tax credit for biodiesel, are all spurring interest and rapid growth in biodiesel technologies in the U.S.
Nearly all biodiesel production from vegetable oil (triglyceride) follows a common set of reaction pathways: first, tranesterification of the triglyceride with excess methanol and NaOH catalyst to give fatty acid ester, which is the biodiesel product; then separation of the ester (+residual oil) liquid phase from the byproduct glycerol (+NaOH) phase; distillation to separate the ester from residual oil; and recovery of pure glycerol as a byproduct. The resulting methyl ester is marketed as an additive to fuel in the U.S., usually about 2% to 20% by volume, and so that the resulting composition is called “biodiesel”. There are oxygenates that can be added to the diesel fuel to promote cleaner burning as well. The uncertainty of a market for large quantities of glycerol from biodiesel and the need for continuous biodiesel production processes are two recognized challenges for large- scale biodiesel implementation.
U.S. Pat. No. 6,890,364 B2 and US2004/0025417 A1 to Delfort et al describe a process for producing glycerol acetals for use in diesel fuels, and they are incorporated herein by reference in their entireties. U.S. published application 2003/0167681 A1, which is also incorporated by reference in its entirety, describes a similar two step process. The process conditions enable the formation of the acetals, with filtration of the solid and catalyst from the composition produced, which is a mixture of acetals. The acetal mixture is added in an amount between 1 to 40%, preferably 1 to 20% by volume to diesel fuel and is soluble in the heating or diesel fuel oils which is important for preventing separation on storage. The acetal additive reduces particulate emissions, particularly from diesel engines and functions like an oxygenate.
U.S. Pat. No. 5,917,059 to Bruchmann relates to a process for forming acetals. Also U.S. Pat. Nos. 6,713,640 and 6,548,681 to Miller et al relate to a process for preparing acetals. Both references are incorporated herein by reference in their entireties.
There is a need for a more direct process for the formation of such glycerol acetals in fuel oil compositions.